Thermal recovery boiler operation dryness is an important parameter, which affects the accuracy of thermal recovery boiler operation safety and the effect of heating oil. In the water / steam two-phase flow dynamic monitoring techniques based on the developed dryness microcomputer measurement and control technology, is to use differential throttling device measuring degree of wet and dry steam flow, and other parameters, with the temperature and pressure sensors will be able to automatic Detection of thermal recovery boiler operation, while the boiler through the feedback control signal to the amount of water and wind to achieve the safe operation of thermal recovery boiler automatically. Key words: dry degree; thermal recovery boiler; thermal oil